A conventional limit switch 6 is shown in FIG. 11 and generally includes a button 61 to control the circuit between “ON” and “OFF” positions. When applied to a machine such as a linear activator which moves in two directions, two limit switches 6 are overlapped as disclosed in FIG. 12 and the two limit switches 6 are controlled by an upper cam 7 and a lower cam 8. The upper and lower cams 7 and 8 are controlled by a shaft 9 cooperated with a gear set 91 so that when the protrusion 71 on the upper cam 7 rotates clockwise to push the button 61 of the upper limit switch 6, the linear activator stops in a first direction, and moves in a second direction. When the protrusion 81 of the lower cam 8 rotates counter clockwise to push the button of the lower limit switch 8, the linear activator stops in the second position and moves toward the first direction.]
However, the overlapped two limit switches 6 make the control unit to have a certain height which may not suitable for some machine. Besides, the two limit switches 6 require more maintenance cost and time.
The present invention intends to provide a limit switch wherein the two operation units are located in the same plane and controlled by a single control member which located between the two operation units so that the height of the whole control unit is reduced.